Note: Descriptions are shown in the official language in which they were submitted.
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SPRAY-DRIED STARCH HYDROLYSATE AGGLOMERATE PRODUCT
AND METHOD FOR PREPARING A SPRAY-DRIED STARCH
HYDROLYSATE AGGLOMERATE PRODUCT
The invention relates on the one hand to a spray-dried starch hydrolysate
agglomerate product. On the other hand, the invention relates to a method for
preparing a spray-dried starch hydrolysate agglomerate product in a spray-
drying
tower, comprising spraying a liquid material onto a solid powder material,
whereby
the liquid material is atomised by means of one or more two-fluid nozzles
using a
fluid for heating and conveying this material, and whereby the agglomerated
spray-
dried starch hydrolysate is produced by injecting the solid powder material in
the top
of the drying tower in such a way that the trajectory of the powder crosses
the spray
pattern of the atomised liquid material.
Starch hydrolysate products are obtained by the partial hydrolysis of cereal,
root or
tuber starches. Depending on the degree of hydrolysis, as expressed by the
dextrose
equivalent (DE), one speaks about maltodextrins (DE < 20) or glucose (corn)
syrups
(DE > 20). These starch hydrolysates can be obtained via different
manufacturing
processes, including a one step enzymatic hydrolysis, a two-step enzyme-enzyme
process or a two-step acid-enzyme process.
Maltodextrins are mainly available commercially in a spray-dried, particulate
form.
Some of the glucose syrups having a DE between 20 and 30 are also available in
a
spray-dried particulate form and are known as "corn syrup solids".
These powder products are used as dispersing aids, flavour carriers, bulking
agents,
humectants, viscosifiers and other functional ingredients. They can work in a
wide
variety of applications - from dry mixes to fillings and from sauces to
beverages.
The physical characteristics of the powder products are of great importance
for their
use in this wide range of applications.
CONFIRMATION COPY
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Important physical properties related to these powders are:
- bulk density (loose and tapped) and related to these, compressibility;
- average particle size;
- particle size distribution;
- mechanical stability;
- flowability;
- dispersability and related to that, dissolution speed.
These physical properties are very important with regard to the handling
properties
of these powder products, but also with regard to their use in a range of
applications.
Today, two major types of starch hydrolysate-based powders are encountered in
the
market.
A first type are the standard spray-dried powders which have a relatively high
bulk
density varying between 0,45 - 0,65 g/cm3, an average low particle size and a
broad
particle size distribution. The relatively high bulk density makes these spray-
dried
powders suitable in the preparation of dry mixes, because phase de-mixing of
the
different components in these compositions is thereby limited or even
prevented.
The relatively high bulk density further results in less voluminous packaging
sizes
thereby influencing positively transportation costs per weight unit. A major
disadvantage however is the relatively high amount of fines (with particle
size < 100
micron), resulting in dusting problems and therefore safety risks, limited or
bad
flowability and increased compressibility.
In addition, these spray-dried powders are difficult to completely hydrate,
i.e. to
dissolve in water. Because of the fine particle size, such powders require
high shear
mixing and low rates of addition to the water, heating or other dissolution
liquid in
order to avoid the formation of small lumps, which are wet on the outside and
dry
within.
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In order to overcome the above cited problems related to dusting and
wetability, a
second type of starch hydrolysates, i.e. spray-dried starch hydrolysate
agglomerated
(powder) products, were developed.
Agglomeration of the starch hydrolysate particles thereby resulted in
increased
particle sizes. The larger, more porous structures thereby increase the void
volume,
and create a lower external surface-to-volume ratio. This improves
flowability,
dispersion and wetability, and also decreases dusting. A drawback to this
treatment is
that it reduces the bulk density of the starch hydrolysate powder products, in
particular the maltodextrin powder products, to values of about 0,15 - 0,4
g/cm3.
Another disadvantage observed is the reduced mechanical stability.
Different processes are known for preparing such spray-dried starch
hydrolysate
agglomerate products. Standard prior art agglomeration processes are for
instance
described in Food Product Design (May 1997): "Spray drying: innovative use of
an
old process" by R.C. Deis, and in Zeitschrift for Lebensmitteltechnik (October
1992): "Recent advances in agglomeration during spray-drying." by E. Refstrup:
In order to compensate for the above cited drawbacks, in US 4,810,307, a
process is
described whereby a spray-dried maltodextrin powder is blended with a volatile
liquid other than water (e.g. 95% ethanol). The resulting blend is then
compacted in a
roller compacter without extraneous lubricant. The formed sheet is then broken
and
sieved. According to the applicant of US 4,810,307, the resulting particles
are non
spherical, do have a bulk density comparable to the starting material, a good
solubility and no flow or dusting problems.
However, particle size distribution is quite broad, while the percentage of
particles
larger than 500 micron (+ 30 mesh) is much too high, as shown in example 2 of
US
4,810,307. Indeed, too large quantities of such large particles result in
"white spots"
in the applications and this is an undesirable effect. In addition,
compressibility of
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the resulting powders is quite high, thereby influencing negatively handling
properties related to storage and transportation of the powders.
Apart from these disadvantageous properties, it is clear for a man skilled in
the art
that the use of liquids such as ethanol creates some safety constraints during
the
manufacturing process.
An alternative is offered by the products obtained via the process disclosed
in US
3,706,598. In this patent application, solid, glass-like starch hydrolysate
products
having a DE of from about 10 to about 25, a water content of less than 15% by
weight and a bulk density of at least about 0,65 g/cm3 (40 pounds per cubic
foot) are
produced by concentrating a hydrolysed starch conversion liquor, heating the
liquor
in a plate heat exchanger, superheating minute droplets of the liquor and
cooling to
solidification. The applicant of US 3,706,598 discloses that the corresponding
products have excellent wetability and solubility in water. However, no
concrete
figures are provided. Furthermore, the density of the products obtained varies
between 0,65 - 0,9 g/cm3 (SS pounds per cubic foot). Because of the fact that
in the
process as described in this patent application, the solidified product is
ground or
milled to an extent sufficient to pass through a 20 mesh screen, it is obvious
for a
man skilled in the art that this results in a disadvantageous quite broad
particle size
distribution, while the percentage of particles which are larger than 500
micron is too
high. In addition, the moisture content of the products disclosed is too high
while the
described manufacturing process is less attractive.
As already indicated above, the compacted powders and the glass-like products
obtained by these processes do show one or more shortcomings which are related
to
their physical properties (density, mechanical stability, particle size and/or
moisture
content) and to the processes used for their manufacture.
The methods disclosed hereunder are related to the preparation of spray-dried
pregelatinised agglomerated starch-based products.
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In US 4,871,398, a continuous method is described for preparing pre-
gelatinised
spray-dried starch agglomerate products. This method uses two or more capped,
two-
fluid nozzles of the type described in US 4,208,851. In this process, two or
more
spray-cook nozzles (or two-fluid nozzles) are aligned in a drying tower such
that
5 their spray patterns intersect. The point of intersection has to be distant
enough from
the nozzles to avoid globbing or clumping and close enough to the nozzles so
that the
surface of the particles are tacky enough to effect adhesion and a build-up of
agglomerates.
In US 4,208,851, a process and an apparatus are described for cooking or
gelatinising
a material which is normally difficult to cook and spray dry because of the
formation
of high viscosities during cooking, so that an easily dryable, uniformly
cooked and
finely-sized product is obtained thereby. The material is initially mixed in
an aqueous
solvent (a slurry is formed) and then atomised into an enclosed chamber to
form a
relatively fine spray which may be uniformly cooked or gelatinised. A heating
medium (e.g. steam) is interjected into the atomised material in the chamber
to cook
the material. The chamber contains a vent aperture to allow the heated
atomised
material to exit the chamber, with the size and the shape of the chamber and
the vent
aperture being effective to maintain the temperature and moisture content of
the
material for a period of time sufficient to cook and gelatinise the material.
In EP 1 166 645, agglomerated spray-dried starch based products and dry-mixes
based on these agglomerated spray-dried starch based products are described.
The
agglomerated starch-based product is a homogeneous powder wherein each powder
particle is an agglomeration of randomly distributed fine grains. As described
in EP 1
166 645, these spray-dried agglomerated starch-based products can be prepared
by
spray-cooking of unmodified (native) or modified starch and maltodextrin in an
apparatus such as is described in US 4,280,851. In the process as described in
EP 1
166 645, the maltodextrin is injected in the top of the spraying tower in such
a way
that the trajectory of the dry powder crosses the spray pattern of the spray-
cooked
starch in order to produce spray-dried agglomerated particles.
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The purpose of the invention is therefore to provide a spray-dried starch
hydrolysate
agglomerate product which combines the advantageous properties of standard
spray-
dried starch hydrolysates and known spray-dried starch hydrolysate agglomerate
products.
This purpose of the invention is obtained by providing a spray-dried starch
hydrolysate agglomerate product, in which the starch hydrolysate has the
following
properties:
- a dextrose equivalent (DE) between 5 and 35;
- a moisture content of < 6% by weight;
- an unpacked bulk density between 0,4 and 0,6 g/cm3;
- a compressibility of less than 10%;
- a particle size distribution whereby less than 5% by weight is bigger than
500
micron and less than 5% by weight is smaller than 53 micron;
- an average particle size of between 150 - 250 micron;
- a mechanical stability of > 95%;
- a static angle of repose (SAOR) of less than 45°, as a measure for
flowability;
and
- a dissolution speed of < 180 seconds.
In this way, a spray-dried starch hydrolysate agglomerate product is obtained
which
has a high bulk density, reduced volume, a high mechanical stability, low
dusting,
high dissolution speed, higher mean particle size and better particle size
distribution.
In a preferred embodiment of a spray-dried starch hydrolysate agglomerate
product
according to the invention, the starch hydrolysate has the following
properties:
- a DE between 5 and 35;
- a moisture content of < 6% by weight;
- an unpacked bulk density between 0,45 and 0,55 g/cm3;
- a compressibility of less than 5%;
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- a particle size distribution whereby less than 3% by weight is bigger than
500
micron and less than 3% by weight is smaller than 53 micron;
- an average particle size of between 175 - 230 micron;
- a mechanical stability of > 97%;
S - a SAOR of less than 40 °; and
- a dissolution speed of < 120 seconds.
In a more preferred embodiment of a spray-dried starch hydrolysate agglomerate
product according to the invention, the starch hydrolysate has a dissolution
speed of
< 90 seconds.
A spray-dried starch hydrolysate agglomerate product according to the
invention
preferably has a DE between of 10 to 22.
Another purpose of the invention is to provide a method for preparing a spray-
dried
starch hydrolysate agglomerate product in a spray-drying tower according to
the
preamble of claim l, whereby the thus obtained spray-dried starch hydrolysate
agglomerate products do show the combined properties of standard spray-dried
starch hydrolysates and known spray-dried starch hydrolysate agglomerate
products,
i.e. a high bulk density, reduced volume, a high mechanical stability, low
dusting,
high dissolution speed, higher mean particle size and better particle size
distribution.
This purpose is realised by providing a method for preparing a spray-dried
starch
hydrolysate agglomerate product in a spray-drying tower, comprising spraying a
liquid material onto a solid powder material, whereby the liquid material is
atomised
by means of one or more two-fluid nozzles using a fluid for heating and
conveying
this material, and whereby the agglomerated spray-dried starch hydrolysate is
produced by injecting the solid powder material in the top of the drying tower
in such
a way that the trajectory of the powder crosses the spray pattern of the
atomised
liquid material, and wherein the liquid material which is atomised by one or
more
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two-fluid nozzles is a starch hydrolysate solution, whereby this starch
hydrolysate
solution is atomised using steam as said fluid.
Although from EP 1 166 645, it is known to inject a maltodextrin powder in the
top
of a spraying tower in such way that the trajectory of this solid powder
crosses the
spray pattern of the spray-cook starch which exits one or more two-fluid
nozzles in
order to produce agglomerated particles, it is not obvious for a man skilled
in the art
to use the two-fluid nozzles to atomise a starch hydrolysate solution on a
solid
powder in order to produce a spray-dried starch hydrolysate agglomerate
product
having the combined properties of standard spray-dried starch hydrolysates and
known spray-dried starch hydrolysate agglomerate products. The two-fluid
nozzles
as described in EP 1 166 645 are used for a totally different purpose, i.e.
spray-
cooking a starch slurry, and not for atomising a maltodextrin solution.
In a preferred method according to the invention, the starch hydrolysate
solution has
a concentration of 50 - 75% dry matter, and more preferably, of 65 - 75% dry
matter.
In an advantageous method according to the invention, the steam has a pressure
between 7 and 15 bar.
The weight ratio of steam versus starch hydrolysate solution (weight
steam/weight
hydrolysate solution) is within the range of 0,05 and 0,4, and preferably
between 0,1
and 0,3.
The heating air which is introduced in the spraying tower has preferably a
temperature between 160 and 300 °C, and more preferably between 180 and
250 °C.
In a preferred embodiment of a method according to the invention, the exiting
air has
a temperature between 90 and 120 °C.
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The ratio between the solid powder and the starch hydrolysate solution, on a
dry
weight basis, is preferably between 0,6 and 1,1, and more preferably between
0,8 and
1.
In a preferred method according to the invention, the dry powder is a starch
hydrolysate powder.
Preferably, the starch hydrolysate powder is a spray-dried form of the starch
hydrolysate solution.
This has the advantage that the starch hydrolysate powder consequently has a
similar
or equal composition as the starch hydrolysate solution.
In an advantageous method according to the invention, the agglomerated spray-
dried
starch hydrolysate particles is brought into a fluidised bed.
Further distinctive features and characteristics will be clarified in the
following
description and the following examples, which should be considered as being no
restriction in the general scope of the invention as that appears from the
above
description and from the claims at the end of this text.
The spray-dried starch hydrolysate agglomerate product according to the
invention,
having the properties as described in the product claims, can be used at the
same time
for preparing dry mixes, as well as for preparing thickening solutions such as
for
meat, dairy, baby food or convenience food applications. In these
applications,
dissolution speed is very important. Improved handling properties with regard
to
bulk density, mechanical stability, dusting properties (safety) and
flowability are of
importance in the preparation of dry mixes, but also with regard to storage,
dosing
and mechanical transportation. As a consequence, such a product will simplify
storage installations and transportation means at the costumer, because only
one type
of product will need to be stored and transported.
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In order to stabilise the above cited starch hydrolysates, they may be
submitted to a
state of the art hydrogenation process prior to the spray-drying step, thereby
providing hydrogenated starch hydrolysates.
5
The properties of the spray-dried starch hydrolysates as described in the
product
claims are determined by means of the methods disclosed herewith:
The term DE (dextrose equivalent) refers to the reducing sugar content of the
10 dissolved solids in a starch hydrolysate, as measured by the Lane-Eynon
constant
titre method. This method is fully described in ISO 5377.
The bulk density of the spray-dried starch hydrolysate agglomerate product is
expressed as the unpacked bulk density. The unpacked bulk density is
determined by
weighing a quantity of spray-dried starch hydrolysate agglomerate product of
the
invention in a glass graduated cylinder of 250 ml. The unpacked density then
corresponds to the ratio of the mass of the product and the volume of the
product.
Packed (tapped) density is then determined by packing the sample under
standard
conditions in an Erweka SVM22 volumeter. Tapped density is then determined
after
50 strokes. Compressibility is expressed by the formula C = ( 1 - p""t ~ pr) *
100%.
Therein is p""~ the untapped density, and pt the tapped density, as defined
above.
Particle size distribution is determined by sieving SO g of powder in a Retsch
VE1000 shaking device containing sieves of 53, 100, 200, 300 and 500 micron,
during 10 minutes using an amplitude of 1,5.
Average particle size is expressed as the mathematical mean particle size on
weight
basis of the different fractions obtained from the particle size distribution.
Mechanical stability is determined on an Alpine sieving apparatus 200 LS-N as
the
ratio of the weight of fraction of the spray-dried starch hydrolysate
agglomerate
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product of the invention remaining on a 150 micron Alpine sieve after 30
minutes
sieving and weight of the product on the same Alpine sieve after 5 minutes.
Seiving
is performed at an underpressure of 1500 Pa. The product sample was first
sieved for
3 minutes on an ASTM Retsch sieve of 150 micron in order to remove small
particles.
Flowability is expressed by the static angle of repose (SAOR). The method is
described by ISO 8398:1989. Angle of repose is defined as the maximum angle in
degrees at which a pile of material retains its slope.
Dissolution speed corresponds with the time needed to dissolve 20 g of product
in
200 ml water at 5 °C in a beaker of 400 ml, whereby the mixture is
continuously
stirred with a magnetic stirrer at 300 rpm.
The method according to the invention for preparing a spray-dried starch
hydrolysate
agglomerate product may be performed in a spray-drying tower as disclosed in
EP 1
166 645. However, also other types of spray-drying towers can be used to
perform
the method. The tower which is used in EP 1 166 645 comprises one or more two-
fluid spraying nozzles as described in US 4,280,851.
In the method according to the present invention, in the spray-drying tower, a
starch
hydrolysate is injected in the top of the tower in such a way that the
trajectory of a
solid powder, preferably a dry starch hydrolysate powder, crosses the spray
pattern
of a starch hydrolysate solution which is atomised by one or more two-fluid
nozzles.
The atomising process of the starch hydrolysate solution in the one or more
two-fluid
nozzles is performed by first atomising the starch hydrolysate solution into
an
enclosed chamber, then interjecting steam into the atomised starch hydrolysate
solution in the enclosed chamber and finally enabling the atomised starch
hydrolysate solution to exit the chamber through a vent aperture into the
spraying
tower.
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In this particular process, the stream of fines of the starch hydrolysate
powder which
is injected in the top of the spraying tower is contacted with the sprays from
the two-
fluid nozzles, using conditions allowing the formation of the spray-dried
starch
hydrolysate agglomerate product of the invention.
Important parameters hereby are the concentration and composition of the
starch
hydrolysate to be agglomerated, the weight ratio of steam to hydrolysate
solution, the
steam pressure used in the nozzles, the temperature of the heating air in the
spraying
tower in which the particles are sprayed, the ratio between the starch
hydrolysate
powder injected in the top of the drying tower and the starch hydrolysate
solution fed
via the two-fluid nozzles, the feeding rate and the angle under which the
spray
patterns intersect.
The starch hydrolysate solution is thereby introduced in the two-fluid nozzles
at a
concentration of 50 - 75%, preferably 65 - 75% dry matter, while the weight
ratio of
steam to starch hydrolysate solution may vary between 0,05 and 0,4, preferably
between 0,1 and 0,3. Steam pressure used may vary between 7 and 15 bar, while
the
temperature of the heating air which is introduced in the spraying tower is
situated
between 160 and 300 °C, more preferably between 180 and 250 °C.
The temperature
of the exiting air at the bottom of the spraying tower is between 80 and 125
°C, more
preferably between 90 and 120 °C. The angle under which the spray
patterns
intersect will be such that contact of the particles occurs at a location
where the
particle surface is tacky enough to promote adherence of the particles, but
not so
close to the nozzle vent apertures that lumping of the spray-dried starch
hydrolysate
agglomerate product occurs. A.o. this angle will depend on the concentration
and
composition (DE) of the starch hydrolysate solution, on the circulating air
temperature, on feed rate through the nozzles and on the ratio between the
starch
hydrolysate powder which is injected in the top of the spraying tower and the
starch
hydrolysate solution that is fed through the two-fluid nozzles. An
advantageous ratio
on dry weight basis is between 0,6 and 1,1, preferably between 0,8 and 1. The
spray-
dried starch hydrolysate agglomerate product can then be brought in a
fluidised bed,
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where the powder is further dried and/or cooled and fines present removed via
the air
stream.
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Example 1:
In this example, the advantageous properties of the product of the invention
are
illustrated by comparing a number of its properties with spray-dried starch
hydrolysate agglomerate products currently commercialised.
Following commercially available products were tested:
Glucidex 21IT from Roquette Freres, C*Sperse 01321 from Cerestar Holding BV
and Granadex SPG20 from AVEBE.
Different parameters are shown in Table 2.
Glucidex C*Sperse Granadex Product
21IT 01321 SGP20 of
the invention
Loose p (g/1)400 474 358 486
Tapped p (g/1)435 504 418 S00
Compressibility8% 6% 14% 3%
PSD (% w/w)
> 53~. > 99 94 91 > 99
> 200 72 40 28 49
> 500 6 2 2 2
Average PSD 270 185 155 220
(~)
SAOR 42 40 60 - 70 36
Mechanical 95% 93% 83% > 98%
stability
Dissolution 230 205 390 55
speed
(sec)
Table 2
PSD: particle size distribution SAOR: static angle of repose
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Example 2:
In this example, dissolution speed at two different temperatures (5 °C
and 22 °C) was
compared of products of this invention versus state of the art products (see
table 3).
Non-agglomerated maltodextrins ( 18DE and 21 DE), as well as agglomerated
5 counterparts (C*Sperse 01318, C*Sperse 01321, Glucidex IT21) are compared
with
products of the invention.
Speed (sec) at 22 Speed (sec) at 5
C C
18DE invention 115 120
21DE invention 50 SS
Standard 18DE 390 540
Standard 21DE 320 S00
Agglomerated:
Glucidex IT21 185 230
C*Sperse 01318 190 205
C*Sperse 01321 175 240
Table 3
10 Results of this example clearly show the outstanding dissolution speed,
compared to
products already considerd as having excellent dissolution properties.
Example 3:
15 Dissolution properties of the spray-dried starch hydrolysate agglomerated
products of
the invention and other spray-dried starch hydrolysate agglomerated products
were
compared to the values disclosed in US 4,810,307 (see table 4). This patent
application describes a process for improving solubility of maltodextrins
while
retaining relatively high densities. Solubility was expressed as the time
needed to
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dissolve 1 g of product in 240 ml water, without stirring. Values disclosed in
US
4,810,307 varied between 5,5 minutes and 9 minutes.
In table 4, these results are compared with a product of the invention and
with
commercially available products.
S
Solubility (minutes)
18DE product of the invention3,5
US 4,810,307 products 5,5 - 9
standard maltodextrin 15DE > 12
agglomerated C*Sperse 01318 S,5
agglomerated Glucidex IT21 6,8
Table 4
From the above, it is clear that the products of the invention clearly show an
improved solubilisation speed.
